This invention relates to an apparatus and a method for facilitating the connection of pipes, and more particularly, but not exclusively, to a powered drill pipe tong for facilitating the connection of sections or stands of drill pipe.
Drill pipe tongs are commonly used for facilitating the connection of sections or stands of drill pipe to a pipe string. Typically, the pipe string hangs in a wellbore from a spider in a floor of an oil or gas rig.
A section or stand of drill pipe to be connected to the pipe string is swung in from a drill pipe rack to the well centre above the pipe string. A pipe handling arm may be used to guide the drill pipe to a position above the pipe string. A stabbing guide may then be used to align a threaded pin of the drill pipe with a threaded box of the pipe string. A drill pipe tong is then used to tighten the connection to a torque of typically 68,000 Nm (50,000 lb.ft).
The drill pipe tong is also used for disconnecting drill pipe. This operation involves breaking the connection which requires a torque typically greater than the tightening torque which may typically be in the order of 110,000 Nm (80,000 lb.ft).
A drill pipe tong generally comprises jaws mounted in a rotary which is rotatably arranged in a housing. The jaws are moveable relative to the rotary in a generally radial direction towards and away from an upset part of the pipe to be gripped. The upset parts of the pipe are generally located above the pin and below the box of the pipe and have an enlarged outer diameter and/or a reduced inner diameter.
In use, the rotary is rotated forcing the jaws along cam surfaces towards the upset part of the section of pipe. Once the jaws fully engage the upset part, the rotary carries on rotating applying torque to the threads and hence tightens the connection between the section of pipe and the pipe string.
Several problems have been observed with such prior art drill pipe tongs.
In particular, such drill pipe tongs can badly scar the upset part of the pipe, particularly if the jaws start rotating relative to the drill pipe.
Once scarred, the pipe is then lowered into the wellbore. Friction between the wellbore (or casing lining the wellbore) and the scarred upset grinds the upset, reducing the diameter.
Scarring of the upset may also be caused by having to reapply the jaws. This is especially common when connecting pipe with xe2x80x9cwedge threadsxe2x80x9d which requires approximately 80xc2x0 of turn in order to toque the connection. Many prior art wrenching tongs need to be reapplied to the pipe every 25xc2x0.
A reduction in diameter of the upset requires the use of a new drill pipe tong or for the old drill pipe tong to be modified therefor.
An attempt at solving this problem is disclosed in PCT Publication Number WO 92/18744, which discloses a rotary comprising hydraulically operated active jaws and stationary passive jaws. The hydraulically activated jaws are engaged fully with the pipe prior to rotation of the rotary, thereby substantially reducing scarring. A hydraulic circuit is provided on the rotary for actuating the jaws. A plunger is used to activate the hydraulic system by depressing a hydraulic piston of the hydraulic circuit repeatedly. This operation takes time, If several seconds can be saved per connection, the overall cost of the construction of an oil or gas well can be drastically reduced, as long as reliability is not sacrificed. Another problem associated with the rotary disclosed in PCT Publication Number WO 92/18744 is that repeated depressing of the plunger for engaging the jaws fully with the pipe may itself cause some scaring.
The present invention provides an apparatus for facilitating the connection of pipes which apparatus comprises a rotary and jaws, characterised in that all of said jaws are active and are actuable by pressurised fluid.
Other aspects of the invention are set out in claims 2 to 14.
There is also provided a method for facilitating the connection of pipes, the method comprising the steps of actuating the jaws of an apparatus in accordance with the present invention with pressurised fluid so that the jaws engage with a pipe at a central axis of the rotary thereof, rotating said pipe to a predetermined torque, and disengaging said jaws, preferably with said pressurised fluid.